The US walked away from a divisive and bloody war in which some 58,000 Americans were killed, along with up to 250,000 South Vietnamese allies and an estimated 3 million communist fighters and civilians.

Thousands of Vietnamese, including war veterans in uniform, lined up to watch soldiers and traditional performers parade through the streets of what is now Ho Chi Minh City.

On April 30, 1975, North Vietnamese tanks rolled into Saigon, then the capital of South Vietnam.

They crashed through the gates of the presidential palace and hoisted the communist flag. It was an incredible victory for the revolutionary forces that had waged guerrilla warfare against the powerful, better equipped United States.

"The tank crashing the gates ... was a symbol of victory for the Vietnamese nation and the Vietnamese People's Army, marking the end of the 30 years of national resistance against the French and then the Americans," said Nguyen Van Tap, 64, who drove Tank 390 through the iron bars and reunited with members of his tank company.

"For the Vietnamese, April 30 is a day of festivities and national reunification."

For the US and its South Vietnamese allies, the day was one of panic, chaos and defeat known simply as the fall of Saigon.

After the government's parade and celebratory speeches were over today, a group of former US Marines who helped Americans evacuate Saigon as it fell planned to gather at the site of the old US Embassy, now the US Consulate.

They were dedicating a plaque to the two fallen comrades who were last two US servicemen killed in the war - Cpl Charles McMahon and Lance Cpl Darwin Judge died on April 29, 1975, when their post near the airport was hit by a rocket.

"We lost ... and I felt that way for a long time," said Kevin Maloney, one of the last Marines out.

"I was ashamed that we left people behind like that. I did what I could, so I'm satisfied with my own performance, but as a nation, I think we could have done better. And I hope we can learn from that, but I don't think we've seen that."

Hundreds of thousands of Vietnamese fled the south in the days and years following the war, with many taking fragile boats in search of freedom.

The majority ended up resettling in the US. Many have since come home to visit family and to invest in the country, but some have remained feverishly anti-communist and have refused to return as long as the one-party government is in power.

The country still tightly controls the press and cracks down on political dissidents. It jails those who dare to speak out for democracy, including in blogs on the Internet.

But much has changed since the early days after the war when Vietnam was plunged into severe poverty and isolation during failed collective farming policies.

The US normalised relations with Vietnam in 1995. More than 16,000 Vietnamese students now study in America, and the US has become one of Vietnam's biggest foreign investors. Bilateral trade exceeded 36 billion US dollars (£23.3 billion) last year.

The two countries have also hosted high-level visits, and Vietnam has welcomed military co-operation and visiting US naval ships.

China continues to spar with Hanoi and other neighbours over disputed islands in the South China Sea in what is viewed as a growing maritime threat in the region.

Today, Ho Chi Minh City is alive with capitalism, and many of the scars from the war are no longer visible on the surface.

It is the economic muscle of the country, and recent and ongoing construction projects have transformed its skyline into glassy high-rises bathed in neon lights.

But much of the old traditions remain. The pavements are still filled with generations of families hustling out of small shops to earn money while elderly women sell the country's famous pho noodle soup from street stalls.